The present invention relates to a component functioning with a reflected acoustic wave wherein a substrate body is provided having at least one reflector on the substrate body with reflector fingers disposed at an oblique angle, an input transducer on the substrate body exciting the acoustic wave, and at least one output transducer on the substrate body for receiving acoustic waves.
A filter functioning with reflected acoustic waves is described on the basis of FIG. 7 in German patent application No. P 31 21 516.5 which corresponds to U.S. Ser. No. 377,466, now U.S. Pat. No. 4,427,954, incorporated herein by reference. This filter, in addition to having an input transducer for exciting an acoustic wave in the surface of a substrate body and an output transducer for converting the received acoustic wave also has two reflector structures which have reflector fingers aligned at a respectively oblique angle. The oblique direction of the reflector fingers of the two structures is selected such that the acoustic wave first impinging on the first reflector structure in its primary wave propagation direction from the input transeucer is deflected at an essentially right angle by reflection such that the reflected wave continues in a new primary propagation direction which is essentially orthogonal to the initial primary wave propagation direction. A further deflection caused by reflection occurs in the second reflector structure to create another new primary wave propagation direction along which the acoustic wave now reflected twice proceeds toward the output transducer. In this context, it should be pointed out that given the existence of an anisotropy of the material of the substrate body this applies for example to lithium niobate which is frequently employed), 90.degree. reflections occur when the reflector fingers of the reflecting structure are disposed at an angle relative to the primary wave propagation direction which deviates somewhat from 45.degree.. This is a correction technique well known to one skilled in the art which is to be applied to the invention described in greater detail below, but which shall no longer be discussed in greater detail here. It shall likewise no longer be discussed in detail that as also shown in FIG. 7 of the earlier application, the reflectors need not be entirely filled out with reflector fingers, and/or the reflector fingers are weighted as is described, for example, in earlier German patent applications Nos. P 32 09 942.7 and P 32 09 962.2. It likewise does not seem necessary to point out here that such reflector structures can be realized not only by means of electrode strips applied to the substrate surface, but can also be realized by means of strip-like troughs or trenches introduced into the substrate surface or by means of dot elements (dots) applied in the linear direction. Such dots can in turn be metallizations applied dot-wise or spot-wise to the surface or can be trenches in the surface.
A further electronic component functioning with reflected acoustic waves wherein the present invention can likewise be employed is disclosed in FIG. 7 of German patent application No. P 31 21 516.7, incorporated herein by reference.
In the usual case, a piezo-electric substrate body which has an essentially oblong shape is provided for electronic components functioning with acoustic waves. In order to avoid disruptions due to reflections occurring at the narrow sides, the substrate body has long been given the shape of a parallelogram which has mutually parallel edges at the long sides. A material for damping acoustic waves referred to as an acoustic sink is also frequently provided at the oblique, narrow sides of the substrate body.